1. Field of the Invention
The present invention relates to a perpendicular magnetic recording head including at least an inductive magnetic transducer for recording, and a method of manufacturing the perpendicular magnetic recording head, and a magnetic recording apparatus including a perpendicular magnetic recording head.
2. Description of the Related Art
In recent years, an improvement in performance of a thin film magnetic head which is included in a magnetic recording apparatus such as a hard disk drive has been sought in accordance with an increase in the areal density of a magnetic recording medium (hereinafter simply referred to as “recording medium”) such as a hard disk. As recording systems of the thin film magnetic head, for example, a longitudinal recording system in which a signal magnetic field is oriented in an in-plane direction (a longitudinal direction) of a recoding medium and a perpendicular recording system in which a signal magnetic field is oriented in a direction orthogonal to a surface of the recording medium are well known. At present, the longitudinal recording system is widely used, but in consideration of market forces in accordance with an improvement in areal density, it is assumed that the perpendicular recording system instead of the longitudinal recording system holds promise for the future, because the perpendicular recording system can obtain advantages that higher linear recording density can be achieved and that a recording medium on which information is recorded is not easily affected by thermal decay.
The perpendicular recording system thin film magnetic head (hereinafter simply referred to as “perpendicular magnetic recording head) includes, for example, a thin film coil generating a magnetic flux for recording, and a main pole layer extending from an air bearing surface to the rear and guiding the magnetic flux to a recording medium so that the recording medium is magnetized in a direction orthogonal to a surface of the recording medium. In the perpendicular magnetic recording head, the recording medium is magnetized by a magnetic field for recording (a perpendicular magnetic field), so information is magnetically recorded on the recording medium.
As the perpendicular magnetic recording head, for example, a perpendicular magnetic recording head including a main pole layer disposed so as to extend in a direction orthogonal to the air bearing surface is known. The perpendicular magnetic recording head of this kind is generally called “single pole type head”. As a specific structure of the single pole type head, for example, a structure in which an auxiliary pole layer for containing an auxiliary magnetic flux is connected to a main pole layer in order to improve overwrite characteristics through increasing the strength of a perpendicular magnetic field is known (for example, refer to Japanese Unexamined Patent Application Publication Nos. H02-066710 and 2002-197615). However, as described above, the single pole type head has an advantage that the overwrite characteristics can be improved, and on the other hand, it is said that the single pole type head has a limit to improving the recording density of the recording medium.
Therefore, as a recent perpendicular magnetic recording head, for example, in order to improve the recording density of the recording medium through preventing the expansion of a recording track width, a perpendicular magnetic recording head including a main pole layer extending in a direction orthogonal to the air bearing surface as described above and a write shield layer preventing the spread of the magnetic flux emitted from the main pole layer is becoming a mainstream. The perpendicular magnetic recording head of this kind is generally called “shield type head”. The write shield layer extends from the air bearing surface to the rear so as to be separated from the main pole layer by a gap layer on a side closer to the air bearing surface. As a specific structure of the shield type head, for example, a structure in which a write shield layer is disposed on a trailing side of a main pole layer is known (for example, refer to Japanese Unexamined Patent Application No. 2001-250204 and EP Patent Application No. 0360978). In a shield type head including the write shield layer, the gradient of a perpendicular magnetic field becomes steeper through preventing the spread of the magnetic flux emitted from the main pole layer, so the recording density of the recording medium can be improved.
In order to secure recording characteristics of the shield type head, for example, in order to stably execute a recording operation, it is necessary to sequentially record new information on the recording medium while maintaining information already recorded on the recording medium. However, in a shield type head in a related art, there is a problem that information recorded on the recording medium may be erased without intention at the time of recording information mainly because of a structural factor that the auxiliary pole layer is connected to the main pole layer. More specifically, in the shield type head in the related art, when a magnetic flux contained in the auxiliary pole layer does not pass through the main pole layer, and is directly emitted from the air bearing surface to outside, an unnecessary magnetic field is generated on the basis of the magnetic flux, so due to the unnecessary magnetic field, information recorded on the recording medium is erased without intention. Therefore, in order to secure the recording performance of the shield type head, even in the case where the auxiliary pole layer is connected to the main pole layer, it is desired to establish a technique for minimizing the possibility of erasing information recorded on the recording medium without intention. In this case, in particular, it is important to secure the strength of a perpendicular magnetic field while preventing information erasing without intention.